The present invention relates to a constructional unit for a heat exchanging device, in particular for motor vehicles. Constructional units of this type are known from the prior art. The constructional units typically have a heating device for air and an evaporator in order thereby to ensure an air conditioning of a vehicle interior. The prior art discloses solutions in which the air passing through the individual constructional units is subsequently conducted through all the individual devices, that is to say, in particular, the heating device and the evaporator. Although these constructional units operate satisfactorily, the routing of the air through all the devices may lead to power losses.
Furthermore, the heating or air conditioning systems are becoming increasingly more compact, as a result of which, in the units according to the prior art, the mixing zones are influenced to an ever greater extent, since the individual heat exchanger devices are arranged one behind the other with respect to the direction of flow of the air.